Lead acid accumulators are widely used to convert chemical energy into electrical energy and conversely, to store electrical energy. The lead acid accumulators generally consist of positive and negative electrodes and electrolyte--sulfuric acid, housed in a hard rubber or plastic case.
The disadvantages of standard lead acid accumulators are well known. Lead acid accumulators require routine filling of their cells with water. The lead acid accumulators are relatively large and heavy for the amount of electrical energy, which they accumulate.
Electrical accumulators having a negative electrode made of iron, cadmium, magnesium, indium or zinc, a positive electrode made of lead dioxide, and electrolyte, which includes an aqueous solution of an alkaline hydroxide and a metallic sulfate, are also known. The alkaline accumulator is inherently limited because its operation depends on an alkaline electrochemical reaction with a salt that forms a weak electrical linkage with the positive electrode.
Consequently, the alkaline accumulator has a relatively small specific power output and must be made relatively large and heavy to produce a given amount of electrical energy.
Thus, there is a need for a hermetically sealed dry accumulator, having a significantly larger power output per unit of mass and a proportionately smaller volume. Ideally, the improved accumulator would contain relatively less lead, would weigh considerably less than conventional accumulators and would demonstrate a longer service life. An accumulator that contains less lead would be simpler to make and would involve the production of less environmentally damaging byproducts.